Bug: Errors surfaced when Highlighting

I have tried highlighting, removing the highlighting and using the 'Erase' button on the highlighting tab but it seems that I am unable to use the 'Undo' and 'Redo' options.  Using the shortcuts does not work either.

I have also realized that using the 'Erase' button on the whole highlighted area would delete the note made but the note remains if I right click the highlighted area and choose 'Remove Highlighting'.

• not sure if this one is intentional though